KR102674057B1 - Mold for casting and manufacturing method of boding wire using the same - Google Patents

Abstract

The present invention provides a new casting mold that suppresses the generation of wire surface scale (inclusions) during the melting/casting process by changing the structure; and a bonding wire method that can minimize wire disconnection defects and increase manufacturing yield using the same.

Description

Casting mold and method of manufacturing bonding wire using the same {MOLD FOR CASTING AND MANUFACTURING METHOD OF BODING WIRE USING THE SAME}

The present invention provides a new casting mold that suppresses the generation of wire surface scale (inclusions) during the melting/casting process by changing the structure; and a bonding wire method that can minimize wire disconnection defects and increase manufacturing yield using the same.

In general, bonding wires are manufactured in the form of wires with a certain diameter by continuously performing processes such as melting, drawing (drawing), heat treatment, and winding of conductive metal materials.

During the drawing process, as the conductive metal material passes through the dies, its diameter decreases and its length increases. At this time, if impurities such as inclusions are present on the surface of the conductive metal material, stress is concentrated and causes disconnection defects in the material. These defects occur when scale (inclusions) generated during the melting/casting process remain on the surface of the metal material. In particular, there is a problem in that disconnection defects occur more frequently in wires with a diameter of 1.5 ㎛ or less.

The present invention was developed to solve the above-mentioned problems, and by changing the structure of the casting mold, it is possible to suppress the generation of wire surface scale (inclusions) during the melt casting process, minimize wire disconnection defects, and increase manufacturing yield at the same time. Mold; The technical task is to provide a method of manufacturing a bonding wire using the same.

Other objects and advantages of the present invention can be more clearly explained by the following detailed description and claims.

In order to achieve the above-described technical problem, the present invention provides a casting mold for continuously manufacturing a conductive wire from a conductive metal melt, including a mold frame portion; and a hollow portion formed inside to penetrate the upper and lower surfaces of the mold frame portion, wherein the first diameter of the hollow portion located on the upper surface of the mold frame portion and the second diameter of the hollow portion located on the lower surface of the mold frame portion are Provided are casting molds for manufacturing bonding wires that have the same characteristics as each other.

For example, in one embodiment of the present invention, the cross section of the hollow portion may be formed uniformly from the upper surface of the mold frame portion to the lower surface of the mold frame portion.

For one embodiment of the present invention, the first diameter and the second diameter of the hollow portion may be Φ8 to Φ8.1.

In addition, the present invention relates to a method of continuously manufacturing a bonding wire from a conductive metal material through a melt casting process, a wire drawing process, a heat treatment process, and a winding process, wherein the melt casting process includes (i) forming a hollow interior so as to penetrate the upper and lower surfaces; Manufacturing a mold including a formed mold frame portion, wherein the cross section of the hollow portion is formed uniformly from the upper surface to the lower surface of the mold frame portion; and (ii) manufacturing a conductive wire by dissolving a conductive metal material and then putting it into the casting mold and cooling it.

For one embodiment of the present invention, the conductive metal may be one or more noble metal materials selected from the group consisting of gold, silver, platinum, and ruthenium.

For one embodiment of the present invention, the conductive metal may have a purity of 99.9% or more.

For one embodiment of the present invention, the cross-sectional diameter of the hollow part included in the casting mold may be Φ8 to Φ8.1.

For one embodiment of the present invention, the manufacturing method includes the steps of (iii) first drawing the bonding wire to a predetermined diameter; (iv) performing primary heat treatment on the primary drawn bonding wire under an inert atmosphere; (v) secondary drawing of the primary heat-treated bonding wire to a desired diameter; (vi) secondary heat treatment of the secondary drawn bonding wire under an inert atmosphere; and (vii) winding the secondary heat treated bonding wire.

For one embodiment of the present invention, the manufacturing method further includes, between step (vi) and step (vii), (vi-1) coating an organic material on the secondary heat treated bonding wire. can do.

According to one embodiment of the present invention, wire breakage defects can be minimized and manufacturing yield can be increased by developing/applying a casting mold with a new structure that suppresses the generation of wire surface scale (inclusions) during the melting/casting process of the bonding wire. .

The effects according to the present invention are not limited to the contents exemplified above, and more diverse effects are included in the present specification.

1 is a cross-sectional view of a casting mold according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of a conventional casting mold.
Figure 3 is an optical microscope image of the wire of Example 1 manufactured using a casting mold according to the present invention.
Figure 4 is an optical microscope image of the wire of Comparative Example 1 manufactured using a conventional casting mold.
Figure 5 is a FE-SEM image of the wire of Example 1 manufactured using a casting mold according to the present invention.
Figure 6 is a FE-SEM image of the wire of Comparative Example 1 manufactured using a conventional casting mold.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified into various other forms, and the scope of the present invention is limited to the following examples. It is not limited to examples. At this time, the same reference numerals refer to the same structure throughout this specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings that can be commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly specifically defined.

In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, so the present invention is not necessarily limited to what is shown. In the drawing, the thickness is enlarged to clearly express various layers and areas. And in the drawings, for convenience of explanation, the thicknesses of some layers and regions are exaggerated.

In addition, throughout the specification, when a part is said to "include" a certain component, this means that it may further include other components rather than excluding other components, unless specifically stated to the contrary. In addition, throughout the specification, “above” or “on” means not only the case where it is located above or below the object part, but also the case where there is another part in the middle, and it must be in the direction of gravity. It does not mean that it is located above the standard. Also, in the present specification, terms such as “first” and “second” do not indicate any order or importance, but are used to distinguish components from each other. And, when a component is described as being 'connected', 'coupled' or 'connected' to another component, the component is not only directly connected, coupled or connected to that other component, but also It can also include cases where other components are 'connected', 'combined', or 'connected' due to another component between them. And throughout the specification, when we say “on a plane,” this means when the target part is viewed from above, and when we say “on a cross section,” it means when we look at a cross section cut vertically from the target part from the side.

Additionally, as used herein, “preferred” and “preferably” refer to embodiments of the invention that may provide certain advantages under certain circumstances. However, under the same or different circumstances, other embodiments may also be preferred. Additionally, mention of one or more preferred embodiments does not mean that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

<Casting mold>

An example of the present invention is a casting mold, specifically a casting mold used in the melt casting step during the bonding wire manufacturing process.

This casting mold includes a hollow portion formed inside to penetrate the upper and lower surfaces of the mold frame portion, and has a straight structure in that the first and second diameters of the hollow portions located on the upper and lower surfaces are equal to each other, so that as it moves toward the lower surface, It is differentiated from the prior art in that it includes a tapered hollow portion shown in Figure 2 below with a larger diameter.

1 is a cross-sectional view schematically showing the structure of a casting mold according to an embodiment of the present invention.

Referring to FIG. 1, the casting mold 100 is a casting mold for continuously manufacturing a conductive wire from a conductive metal melt, and includes a mold frame portion 10; and a hollow portion 11 formed inside to penetrate the upper and lower surfaces of the mold frame portion 10, and a first diameter 10a of the hollow portion 11 located on the upper surface of the mold frame portion 10. and the second diameter 10b of the hollow portion located on the lower surface of the mold frame portion 10 have the same structure.

The casting mold 100 may be made of common materials known in the art and is not particularly limited. For example, it may be made of ceramic material, metal, or metal alloy.

In addition, the casting mold 100 includes a hollow portion 11 formed inside to penetrate the upper and lower surfaces of the mold frame portion 10, and has a first diameter 10a and a first diameter 10a of the hollow portion 11 located on the upper and lower surfaces, respectively. 2 As long as the diameters 10b are the same, there is no particular limitation on the size, structure, and/or shape of the mold 100.

For example, the cross section of the hollow portion 11 may be formed uniformly from the upper surface of the mold frame portion 10 to the lower surface of the mold frame portion 10. The cross section of the hollow portion 11 exhibits a straight structure with substantially the same diameter along the thickness direction of the mold frame portion 10.

For another specific example, the first diameter 10a and the second diameter 10b of the hollow portion 11 may be Φ 8 to Φ 8 ± 0.1, and more specifically, it is preferable to be Φ 8. Additionally, the number of hollow parts formed inside the mold frame unit 10 may be one or two or more hollow parts.

The size of the casting mold 100 according to the present invention is not particularly limited and can be appropriately adjusted within the range of typical mold sizes known in the art.

<Method of manufacturing bonding wire>

Another example of the present invention is a bonding wire manufacturing method using the above-described casting mold.

Hereinafter, a method of manufacturing a bonding wire according to an embodiment of the present invention will be described. However, it is not limited to the following manufacturing method, and the steps of each process may be modified or selectively mixed as needed.

In general, wire for semiconductor packages is manufactured through a continuous process of melting/casting, drawing (drawing), heat treatment, and winding. In the present invention, it can be manufactured according to conventional methods known in the art, except for applying a casting mold with a new structure that can suppress the generation of wire surface scale (inclusions) during the melting/casting process.

As an example of the above manufacturing method, a bonding wire is continuously manufactured using a conductive metal material through a melt casting process, a wire drawing process, a heat treatment process, and a winding process, and the melt casting process includes (i) an internal structure so as to penetrate the upper and lower surfaces; manufacturing a mold including a mold frame in which a hollow portion is formed, and the cross-section of the hollow portion is formed uniformly from the upper surface to the lower surface of the mold frame portion ('Step S10'); and (ii) manufacturing a conductive wire by dissolving a conductive metal material and then putting it into the casting mold and cooling it ('step S20').

(i) Casting mold manufacturing step ('S10 step')

The step S10 is a step of manufacturing a casting mold of a predetermined shape for manufacturing a wire.

This casting mold has a hollow portion formed inside it to penetrate the upper and lower surfaces, and as long as the first diameter and the second diameter of the hollow portion located on the upper and lower surfaces are the same, the structure, size, and/or material are not particularly limited.

(ii) Conductive wire manufacturing step ('S20 step')

The step S20 is a step of manufacturing a wire with a certain diameter by pouring the melt of the conductive metal material constituting the wire into the manufactured mold and then cooling it.

The conductive metal material is not particularly limited as long as it is a conductive metal material that can be used as a bonding wire, and specifically, one type selected from the group consisting of metals with excellent electrical conductivity, such as gold (Au), silver (Ag), platinum, and ruthenium. It may be one of the above precious metal materials. More specifically, it is preferably gold (Au) or silver (Ag). Additionally, the conductive metal material may have a purity of 99.9% or higher, specifically 99.99% or higher, and more specifically, 99.999% or higher.

By going through the above-described melt casting step, a conductive rod with a diameter of approximately Φ8 with no surface scale remaining can be manufactured. Additionally, with uniform surface characteristics, wire disconnection defects can be minimized and manufacturing yield can be significantly increased. In particular, a significant increase in manufacturing yield can be achieved in melting/casting precious metals such as gold (Au), silver (Ag), etc.

The wire drawing process, heat treatment process, winding process, etc. performed after the melt casting process can be performed without limitation as a typical bonding wire manufacturing process known in the art, and is not particularly limited to specific methods and/or conditions.

For another example, the manufacturing method includes (iii) first drawing the bonding wire to a predetermined diameter ('step S30'); (iv) primary heat treatment of the first drawn bonding wire under an inert atmosphere ('S40 step'); (v) secondary drawing of the primary heat-treated bonding wire to a desired diameter ('S50 step'); (vi) secondary heat treatment of the secondary drawn bonding wire under an inert atmosphere ('S60 step'); and (vii) winding the secondary heat treated bonding wire ('S70 step').

(iii) Primary freshening stage (‘S30 stage’)

The S30 step is a step of processing the melt-cast conductive wire into a wire shape according to specifications through a drawing process.

The wire drawing (drawing) process is one of the metal processing methods for making wire rods or thin pipes. Metal raw materials are passed through dies with smaller cross-sectional areas and pulled by mechanical force to reduce the cross-sectional area and extend it in the longitudinal direction to form the desired shape. It is a process of transforming into a wire of any size. In other words, a cross-sectional product with the same shape and diameter as the diameter of the die through which the raw material passes is obtained. These drawing processes include hot drawing and cold drawing, and these can be carried out individually or in combination.

For example, if a conductive raw material with a purity of 99.90% or higher is subjected to a primary drawing process using a single die, conductive raw materials with a diameter of Φ8 to 8.1 can be processed to a diameter of 0.35 to 0.1 mm.

At this time, the cross-sectional reduction rate in the first drawing step may be 95 to 99%, specifically 98 to 99%. However, there is no particular limitation thereto, and it can be adjusted appropriately considering the desired size.

(iv) First heat treatment step ('S40 step')

In step S40, the physical properties of the wire that has been hardened by wire drawing are adjusted to be soft by applying continuous heat treatment to the first drawn wire. Additionally, processing stress caused by wire drawing can be removed and cracking can be prevented.

The heat treatment method is not particularly limited, and conventional methods and conditions known in the art can be used. For example, this can be done by passing the wire being transported through a heat treatment facility set at a predetermined temperature. At this time, the heat treatment temperature is not particularly limited and can be appropriately adjusted depending on the wire material used. For example, it may be 200 to 500°C. Additionally, in order to prevent oxidation of the wire, heat treatment can be performed under an inert atmosphere by continuously injecting Ar, nitrogen gas, etc. into the heat treatment facility.

(v) secondary freshening stage (‘S50 stage’)

The S50 step is a step in which a secondary wire drawing process is performed on the primary heat treated wire and processed to the desired diameter.

In the first drawing step, a predetermined diameter is achieved using a single drawing machine, whereas in the second drawing step, a wire with a desired diameter can be manufactured through a continuous drawing facility in which a plurality of drawing dies are arranged.

At this time, the conditions of the secondary wire drawing process are not particularly limited and can be carried out at a line speed of 100 to 200 m/min. Additionally, the cross-sectional reduction rate in the second drawing step may be 50% to 81%, specifically 70% to 81%. However, there is no particular limitation thereto, and it can be adjusted appropriately considering the desired size.

Through the second drawing step, a wire with a diameter of 10 to 100 ㎛, specifically 20 to 100 ㎛, can be obtained.

(vi) Second heat treatment step ('S60 step')

The step S60 is a step of applying heat treatment to the cleaned bonding wire to adjust the physical/mechanical properties to meet the required specifications. That is, by controlling the heat treatment temperature, the breaking load and elongation of the final bonding wire can be adjusted.

Since the temperature range and conditions of the secondary heat treatment step can be applied in the same way as the above-described first heat treatment step, separate description is omitted.

(vii) winding stage (‘S70 stage’)

In step S70, the manufacture of the final product is completed by winding the heat-treated bonding wire into the winding part.

At this time, the winding method is not particularly limited, and a conventional winding machine known in the art can be used. Additionally, spool size, winding direction, and working conditions can be appropriately adjusted according to customer needs.

If necessary, the method for manufacturing a bonding wire according to the present invention includes the step (vi-1) of coating an organic material on the secondary heat treated bonding wire between step (vi) and step (vii) ('S65). step'); may be further included.

The step S65 is a step of forming an organic coating layer on the surface of the final heat-treated wire.

These organic substances are not particularly limited in their composition and content, as long as they can function to prevent cooling and jamming of the wire when applying the final heat treatment process. At this time, if the thickness of the organic coating layer is too thin, the desired effect cannot be achieved. Conversely, if it is too thick, problems such as increased final bonding wire diameter and capillary clogging may occur. Accordingly, it is desirable to adjust the thickness of the organic coating layer formed on the surface of the wire to 500 nm or less, specifically in the range of 200 to 300 nm. In addition, the coating method can also be freely applied as a conventional coating method known in the art.

The bonding wire manufactured through step S65 has an organic coating layer formed after the remaining organic and inorganic impurities are removed through a cleaning process, so it can have uniform characteristics in terms of the composition and thickness of the coating layer.

As described above, the present invention develops a casting mold with a new structure that suppresses the generation of wire surface scale (inclusions) during the melting/casting process and applies it to the bonding wire manufacturing process to minimize wire disconnection defects and increase manufacturing yield. can be increased. In particular, in the present invention, the lower diameter (e.g., second diameter) standard of the casting mold is changed from Φ8.5 to Φ8, and at the same time, the structure of the hollow part is changed to straight, thereby making the metal casting material. Casting can be done at a constant cooling rate and temperature, which not only prevents scale (inclusions) from remaining on the surface of the wire, but also has uniform surface characteristics, minimizing the occurrence of wire disconnection defects. In addition, the present invention can secure a manufacturing yield increase of approximately twice that of bonding wire using a conventional tapered casting mold (see Table 1 below).

The bonding wire of the present invention manufactured as described above can be usefully applied in the semiconductor package field. For example, it can be used as a bonding wire used to connect external leads and chip electrodes of semiconductor devices such as transistors, ICs, and LSIs, and can be applied to various fields that require bonding through wires.

Hereinafter, the present invention will be described in detail through examples. However, the following examples and experimental examples merely illustrate one form of the present invention, and the scope of the present invention is not limited to the following examples and experimental examples.

[Example 1]

Conductive metal materials with a purity of 99.999% or higher were continuously melted and cast at a temperature of 1,100°C or higher using a high vacuum melting furnace. At this time, the casting mold was used with the same upper and lower hole dimensions of Φ8, and was solidified by passing through a cooling jacket to produce a wire with a diameter of Φ8. The fabricated Φ8 wire was confirmed to have surface scale and its components using an optical microscope and an electron microscope (see Figures 3 and 5 below).

Afterwards, single drawing was carried out and the first drawing was carried out to a certain diameter (Φ1~Φ2). Afterwards, heat treatment was performed at a certain temperature (200~500℃) to minimize defects that occurred during the processing process. At this time, inert gas (N ₂ or Ar) was continuously injected into the heat treatment facility to prevent oxidation. Afterwards, using a continuous wire drawing facility consisting of several dies as a set, secondary wire drawing was performed at a line speed of 100~200 m/min to produce a wire with a diameter of 20~100㎛.

After manufacturing was completed, the weight of wire breakage generated during the wire drawing process was measured to confirm the manufacturing yield and is listed in Table 1 below. At this time, as a result of measuring the weight generated due to wire disconnection defects and confirming the manufacturing yield, it was confirmed that when the same mold with the top and bottom specifications of Φ8 was used, the effect was increased by 75% compared to the previous version.

[Comparative Example 1]

Conductive metal materials with a purity of 99.999% or higher were continuously melted and cast at a temperature of 1,100°C or higher using a high vacuum melting furnace. At this time, the casting mold used was a mold with an upper size of Φ8 and a lower size of Φ8.5, and was solidified by passing through a cooling jacket to produce a wire with a diameter of Φ8. The fabricated Φ8 wire was confirmed to have surface scale and its components using an optical microscope and an electron microscope (see Figures 4 and 6 below).

Afterwards, single drawing was carried out and the first drawing was carried out to a certain diameter (Φ1~Φ2). Afterwards, heat treatment was performed at a certain temperature (200~500℃) to minimize defects that occurred during the processing process. At this time, in order to prevent oxidation, inert gas (N ₂ or Ar) was continuously injected into the heat treatment facility. Afterwards, using a continuous wire drawing facility consisting of several dies as a set, secondary wire drawing was performed at a line speed of 100~200 m/min to produce a wire with a diameter of 20~100㎛. After manufacturing was completed, the weight of wire break scrap generated during the drawing process was measured to confirm the manufacturing yield (see Table 1 below).

[Evaluation Example 1]

For the Φ8 wire of Example 1 and Comparative Example 1 manufactured using a casting mold, the occurrence of surface scale and its components were confirmed using an optical microscope and an electron microscope.

Figures 3 and 5 are optical microscope and FE-SEM images of the Φ8 wire prepared in Example 1, respectively, and Figures 4 and 6 are optical microscope and FE-SEM images of the 8 wire prepared in Comparative Example 1, respectively.

When using a new casting mold whose structure has been changed so that the first and second diameters of the hollow portion communicating with the upper and lower surfaces of the casting mold are the same, not only does no scale (inclusions) remain on the surface of the wire, but the wire has uniform surface characteristics. It was confirmed that disconnection defects were minimized.

[Evaluation Example 2]

The results of the melt casting process performed in Example 1 and Comparative Example 1 are shown in Table 1 below.

Comparative Example 1 Example 1 Casting mold schematic diagram Figure 2 Figure 1 Ministry of SMEs and Startups first diameter Φ8 Φ8 second diameter Φ8.5 Φ8 shape taper straight scale
EDS component analysis Gold (Au) 79.10 100 Calcium (Ca) 12.56 - oxygen (O) 8.34 - Casting process Manufacturing yield (%) 48.14 84.09

As shown in Table 1, in the present invention, it was confirmed that by changing the structure of the casting mold, not only was there no scale (inclusions) on the surface of the wire after the melt casting process, but the manufacturing yield was significantly increased by approximately two times.

100, 200: Casting mold
10, 20: Mold frame part
11, 21: CCP
10a, 20a: First diameter of the hollow part
10b, 20b: second diameter of hollow part

Claims (9)

delete delete delete A method of continuously manufacturing a bonding wire using a conductive metal material through a melt casting process, wire drawing process, heat treatment process, organic coating process, and winding process,
The manufacturing method is,
(i) manufacturing a casting mold including a mold frame portion having a hollow portion formed therein so as to penetrate the upper and lower surfaces, and a cross section of the hollow portion being formed uniformly from the upper surface to the lower surface of the mold frame portion;
(ii) manufacturing a conductive wire by melting a conductive metal material and then putting it into the casting mold and cooling it;
(iii) first drawing the bonding wire to a predetermined diameter;
(iv) performing primary heat treatment on the primary drawn bonding wire under an inert atmosphere;
(v) secondary drawing of the primary heat-treated bonding wire to a desired diameter;
(vi) secondary heat treatment of the secondary drawn bonding wire under an inert atmosphere;
(vi-1) coating an organic material on the secondary heat treated bonding wire; and
(vii) winding a bonding wire coated with an organic material;
A method of manufacturing a bonding wire comprising. According to clause 4,
A method of manufacturing a bonding wire, wherein the conductive metal is one or more noble metal materials selected from the group consisting of gold, silver, platinum, and ruthenium. According to clause 4,
A method of manufacturing a bonding wire, wherein the conductive metal has a purity of 99.9% or more. According to clause 4,
The casting mold is,
Mold frame part; and
It includes a hollow portion formed inside to penetrate the upper and lower surfaces of the mold frame portion,
A method of manufacturing a bonding wire, characterized in that the first diameter of the hollow portion located on the upper surface of the mold frame portion and the second diameter of the hollow portion located on the lower surface of the mold frame portion are the same. According to clause 4,
A method of manufacturing a bonding wire, wherein the cross-sectional diameter of the hollow part included in the casting mold is Φ8 to Φ8.1.


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